Reply to Refurb MBP Upgrade Guidance HDD & RAM

Alright so I finally bit the bullet and bought a refurbed late 2011 MBP with 120g SSD. It should be here in a week or so. I want to upgrade the ram and do the optibay. Ive done my research and it seems the best route is to go with crucial/micron ram along with a solid hdd. Im believeing a Scorpio Black. My main concern is reliability. Would there be any reliability issues between a 500g or 750g Scorpio Black? How about the RAM? Any and all input and recommendations are appreciated. Again my main goal is reliability. It doesn't have to be the fastest Mac on the planet. Or the one with the most capacity. Thanks.